This invention pertains generally to radiography and particularly to X-ray spot film apparatus and method of operating same.
It is known in the art of diagnostic X-ray equipment that many different modes of operation are desirable. For example, it may be desirable, inter alia, to change: (a) the size of the photographic film; (b) the number of images on any given photographic film; (c) the positioning of images on any given photographic film. In the past, different modes of operation have been called up by actuating selected sets of switches in a matrix of switches to provide appropriate control signals for each different mode of operation. Unfortunately, the number of switches required in the matrix to provide the appropriate control signals is relatively large. As a result, then, difficulty is encountered in finding room on known spot film apparatus for mounting the matrix of switches. Still further, it will be recognized that the number of different modes of operation is limited by the number of switches in the largest possible matrix of switches.
In order to determine the particular mode of operation that has been selected in any known spot film apparatus, the matrix of switches (or associated indicator lights) must be inspected. When the number of switches in the matrix is large, the probability of error in the setting of individual switches, or in observing associated indicator lights, becomes unacceptably high. An additional problem with so many switches is that the process of setting the switches might be very lengthy. In a medical facility with many doctors, each doctor might require different switch settings. Thus, the operator of an X-ray equipment in such an environment wastes appreciable amounts of time changing the switch settings to meet different requirements.
It is known to use stepping motors in spot film apparatus to provide the motive source for the positioning of elements (such as a film cassette or a mask) within such apparatus. Unfortunately, however, known types of control circuitry include resistors that may, on occasion, dissipate large amounts of heat. Such dissipation obviously is deleterious to proper operation.
It is known to arrange spot film apparatus so that more than one exposure may be made on the film in each cassette. To accomplish such exposures, it is necessary to provide for properly loading the cassette and moving the cassette into the correct position for each exposure. Further, it is necessary to provide an adjustable mask to reduce fogging of the film due to stray radiation. The known mechanisms for accomplishing the foregoing are complicated and susceptible to failure.